1. Field of the Invention
The present invention is related to an apparatus and process for efficiently heating fluids in a vented open system. More particularly, the present invention is directed to a system in which a gas burner flame passes through a tube bundle which is encased in a shell that is filled with a fluid to be heated.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. Sections 1.97-1.99
Many applications require transferring heat from one place to another or from one medium to another. Many types of heat exchangers have been developed for this purpose. Heat exchangers, as used herein, typically transfer, recover, or usefully eliminate heat from a place where it is not needed, without a phase change in either liquid. This heating is accomplished in a number of ways. In industrial applications, it is known to provide a tube and shell heat exchanger in which the shell encloses a tube bundle and a hot working fluid is passed through the tubes to heat a fluid passing through the shell. The fluids are usually water, but either or both can be a gas, such as steam, air or hydrocarbon vapors; or they may be liquid metals, such as mercury or fused salts.
The conventional industrial heat exchanger requires some system outside the heat exchanger to heat the working fluid. Such systems include, for example, boilers, which use a flame to heat a liquid, which may or may not be heated into steam, which is then passed through the tubes in order to heat another liquid that flows through the shell. Other types of system components that are involved in the heating of liquids and that many users would like to eliminate include steam boilers, feed water pumps, condensate receiver tanks, steam to other liquid heat exchanges, hot oil heaters, electric boilers, and plate heat exchangers. Many applications, however, require only heated liquid and many of these complex systems would be omitted if there were a way to omit them.
This arrangement requires expensive, bulky, complex assemblies with high operating and maintenance costs. These features are sometimes avoided by using electricity for heating, electrical heating is expensive and is economically unsuitable in many applications.
Therefore, there is a need for a heat exchanger that is relatively inexpensive to operate, that is relatively simple in design, that eliminates many of the assemblies required in conventional boiler-operated heat exchangers.
Accordingly, it is a primary object of the present invention to provide a heat exchanger that is relatively inexpensive to operate.
It is another object of the present invention to provide a heat exchanger that is relatively simple in design.
It is another object of the present invention to provide a heat exchanger that eliminates many of the assemblies required in a conventional boiler-operated heat exchanger.
These and other objects of the present invention are achieved by providing a gas fired tube and shell heat exchanger in which a gas-fired burner projects its flame directly into the inlet end of a tube bundle and the heat from the flame flows directly through the tube bundle. The tube bundle is sealed within a shell, which is a sealed chamber through which a working liquid, such as water, is circulated and is heated by the hot tubes. Air is forced through the tube bundle by either a draft induction blower located at the outlet end of the tube bundle or a forced draft blower located at the inlet. The burner is a gas-fired burner whose flame is encapsulated in a layer of cool air due to the effect of the induction blower drawing air through the tube bundle from the exhaust outlet, so that the flame does not melt or burn through the tubes. The heat exchanger burner can be fueled by natural gas, methane, propane and the like.
A gas fired tube and shell heat exchanger according to the present invention is used, for example, to heat liquid in a vented open system or a pressurized closed loop system. Liquid that may be heated inside the shell include, but are not limited to, process water, heating water, gray water, waxes, petroleum products, caustic liquids, acids, phosphates, cooking oils, chromates, detergents, beers, alkali solutions, brighteners, and so forth. Any liquid can be heated with the present invention, provided that the liquid can be pumped through the shell. A particularly attractive process includes heating water for circulating through in the cooling systems of certain diesel engines that are used to power emergency or peak demand generators. These engines must be kept hot at all times to prevent untimely deterioration of seals and the like and to allow for maximum power generation immediately upon starting.
Liquid being heated in the shell should be pumped through the shell at a rate allowing for maximum or near maximum heat exchange, and at a rate sufficient to prevent overheating of the tubes, which would cause unwanted deposits on the tubes.
Potential applications of the gas fired tube and shell heat exchanger according to the present invention include but are not limited to, metal finishers, hospitals, laundries, chemical manufacturers, appliance manufacturers, schools, colleges, food processors, drink processors, the petroleum industry, power generation plants, agricultural application and any original equipment manufacturer that uses heated liquids in its processes.
Other objects and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, the preferred embodiment of the present invention and the best mode currently known to the inventor for carrying out his invention.